The present invention relates to a storage system having a plurality of storage devices in a redundant configuration.
Disk array systems having a plurality of disk drives configured based on RAID (Redundant Arrays of Independent Inexpensive Disks) run those disk drives in parallel to process data. For example, when receiving a write command from a host system, these disk array systems add redundant data to the relevant write data, and then distribute and write the data to several disk drives.
On the other hand, when receiving a read command from a host system, these disk array systems read in parallel the relevant data distributed and written to the respective disk drives, and send the read data to the host system. This type of disk array system is provided with a function to carry out error correction using the redundant data and shift to fallback operation if any of the plurality of disk drives configured based on RAID fails. In the fallback operation, because the redundancy level is low, data is normally recovered via correction-copy to a spare disk.
When data recovery to a spare disk is completed and the failed disk drive is manually replaced with a new disk drive, the disk array system copies data restructured in the spare disk back to the new disk drive.
Known references that refer to correction-copy to a spare disk include, for example, Japanese Patent Laid-open Publication No. 2005-38271 and Japanese Patent Laid-open Publication No. H05-314674.